Hundreds of civilians from Saqlawiya district northwest of the city of Fallujah were evacuated on Friday by Iraqi Shia militia, as fighting continued to recapture the district, Al-Alam New Network reports.

Iraqi army, police and Shia paramilitary known as Popular Mobilization Units advanced to the northern and western outskirts of the city of Fallujah, a longtime bastion of the militants of the Islamic State (ISIS / Daesh / ISIL).

Shia militia has already recaptured Garma district, northeast of Fallujah and handed it over to the government forces and advanced to recapture Saqlawiya.

Desperate for food and water, residents fleeing fighting expressed gratitude to Shia fighters who distributed food and water among them.

The assault on Fallujah has begun what is expected to be one of the biggest battles ever fought against ISIS. Fallujah was the first Iraqi city that fell under control of the ultra-hardline Sunni militants, in January 2014.

About 50,000 civilians remain in the city, according to the United Nations.

Fallujah, where U.S. troops fought their biggest battles after the invasion of Iraq in 2003, is the militants' closest stronghold to Baghdad.

Shia militias assisting the army in its offensive have said they will take part only in the encirclement of Fallujah, to avoid fanning sectarian tension.